The effects of CNS stimulation and psychological stress on the physiology and pathology of the heart will be studied. Modifications in ECG, blood pressure, and blood flow associated with CNS stimulation in the cat and environmental stress in the squirrel monkey will be measured. Hearts and other organs will be removed from these animals at the termination of the experiment and examined for pathological changes. Assessment techniques will include standard histological procedures and biochemical analysis of calcium uptake of myocardial tissue and myofibrillar ATPase activity. By careful assessment of these data, the changes in physiological function induced by CNS and environmental stimulation necessary to produce functional disturbances of the myocardium will be ascertained. These investigations will add not only to knowledge about the physiology of cardiac function but also lead to a better understanding of CNS mechanisms and psychological factors that elicit myocardial necrosis and cardiac dyysrhythmias.